The long-term objective of this project is to study the mechanism of differentiation of mouse embryonal carcinoma cells. The clonal cell lines PCC4-F, PCC4-aza-1, and PCao will be used for these studies. Emphasis will be placed on the in vitro differentiation of these cell lines. The specific approaches will be: (1) examination of the influence of embryonal carcinoma cell cytoplasm on the gene expression in differentiated cells and the influence of the cytoplasm of differentiated cells on the multipotentiality of embryonal carcinoma cells, (2) comparison of the properties of the embryonal carcinoma cell with embryonal carcinoma derived lines PFHR-9 and M1536-B3, (3) development of an in vitro myogenic differentiation pathway and (4) exploration of the effect of a limited number of extrinsic factors on the differentiation of the embryonal carcinoma cell.